The present invention relates to a double variable reluctance resolver and a multiple speed resolver system that includes redundant variable reluctance resolvers (or VR resolvers) to improve reliability.
In general, redundancy has been provided to improve the safety and reliability of the VR device. With rotation detection sensors in particular, redundant resolvers have been employed as shown in Japanese Unexamined Patent Application Publication 2001-197610. Two resolvers are structured for a master controller so that they provide redundancy. When one of the resolvers experiences an abnormality, the resolver with the abnormality is released from the control system and the master controller continuously functions using the remaining resolver. However, the structure, position and assembly of the two resolvers are unclear from the drawings, and consequently, the control mechanism for the synchronized operation of the two resolvers is unclear.
As shown in FIG. 7A, a stator winding 101 is formed on each magnetic pole mounted on a stator yoke 102 via a crossover hook 103 in a serial manner. The ends of the stator winding 101 are attached to a connector 104. The salient poles of the rotor 105 are formed in a shape that produces appropriate changes in gap permeance when the rotor 105 rotates. Therefore, the amplitude of the output signal of the stator winding 101 changes and is represented by a sine wave. The circumference of the gap corresponds to one cycle. The number of salient poles of the rotor 105 is seven in the example of FIG. 7A.
Japanese Unexamined Patent Application Publication 2000-018968 shows the structure and position of a resolver that incorporates redundancy. In FIGS. 5A and 6A, structures are shown in which two stators are spaced apart in the axial direction.
A structure having two stators assembled in a prior art motor is shown in FIG. 6A. FIG. 6B is a schematic view of the double resolver system of FIG. 6A. FIG. 6C shows a double resolver of the prior art. FIG. 6D shows a multiple speed resolver system using the double resolver of FIG. 6C and a prior art gear mechanism. FIG. 6E illustrates the relationship between the output signals of the prior art double resolver of FIG. 6D.
In FIG. 6A, a motor structure 115, a second (No. 2) resolver structure and a first (No. 1) resolver structure are arranged in order from the right to left in the casing 106 of the motor. At the center of the casing 106, rotation axis 108 is supported by a bearing 107. On the rotation shaft 108, rotor 109 of the motor, rotor 110 of No. 2 VR resolver, and rotor 111 of the No. 1 VR resolver are axially spaced apart in order from right to left in FIG. 6A. In the casing 106, a stator 112 of the motor, a stator 113 of the No. 2 VR resolver and stator 114 of the No. 1 VR resolver are axially spaced in order from right to left in FIG. 6A in correspondence with the rotors 109, 110 and 111.
FIG. 6B shows the assembled redundant system using the resolvers in FIG. 6A. The No. 1 VR resolver and the No. 2 VR resolver have the same structure. The rotors 110, 111 have the same structure as well and a random nX-times axis angle can be employed.
The multiplied axis angle is defined to be 1X when a single rotation of the rotor can generate a cycle of a sine wave voltage. For example, n (random integer) cycles of the output sine signal that output from the stator secondary winding during one rotation (360°) of the axis is indicated as nX.
There are several types of stator coils. For example, in the case of a one phase excitation with a two phase output, a stator coil includes reference (Ref) windings 121 and 121′ as the primary windings and sine windings 122 and 122′ and cosine windings 123 and 123′ as the two secondary windings. The sine and cosine windings have a phase difference of 90°. A reference signal of sin ωt is input to the sine windings 121 and 121′. Output signals of sin ωt sin θ and sin ωt cos θ, which are modified depending on the rotor rotation angle θ, are obtained for the sine windings 122 and 122′ and cosine windings 123 and 123′.
Resolver-to-digital (R/D) converters 124 and 124′ find sin (θ−φ) from the signals sin φ and cos φ that correspond to the standard rotation angle φ controlled by the voltage controlling oscillator (not shown) and the resolver output signal that includes the rotation angle θ. Phase locked loop (PLL) control is conducted to adjust the count value, which is equivalent to φ, so that the phase difference (θ−φ) becomes zero. At that time, the status when the PLL control converges, namely, φ at the state of (θ−φ)=0, is detected and output as the value of the rotation angle θ of the rotor.
The output of the primary (No. 1) resolver of the R/D converter 124 and the output of the secondary (No. 2) resolver of the R/D converter 124′ in FIG. 6B are compared by the comparator 125. When deviation determined by the comparator 125 is not within a designated range, a failure is determined.
In addition, in order to detect an abnormality of the resolvers and R/D converters 124 and 124′, the reference signal elements of the output signals of the resolver are removed, and detection is conducted to extract the modulating signals sin θ and cos θ that amplify and modulate the reference signals. Between these two modulating signals, in principle, there is a relationship of sin2θ+cos2θ=1. The sum of squares of the sin θ and cos θ, which are extracted through the detection, is calculated. When the sum of squares falls below the designated threshold, abnormality of the resolver output signal is found.
This prior art double resolver system has problems when it is analyzed closely. Japanese Unexamined Patent Application Publication 2000-018968 provides a solution to the problem that, when the resolver coils of the same structure are provided on two stators that coaxially spaced apart, the axial length of the device increases. In the device of FIG. 6C, the resolver coil 130 is structured with at least a double system that includes a first resolver coil 132 and a second resolver coil 133, which are provided on the ring-shaped stator 131. The first resolver coil 132 and the second resolver coil 133 are provided on the ring-shaped stator 131 and are sectioned every 90°, and at the same time, they are provided in a facing position with a 180° difference on the ring-shaped stator 131.
The first and second resolver coils 132 and 133 structures are redundant. For example, the ring-shaped stator 131 maybe attached to a generator of a car engine, and the rotor 134 may be connected to the rotation axis of the generator. The rotation status of the generator is detected by the first resolver coil 132 as a difference in voltage, as is widely known in the art. If the first resolver coil 132 fails due to disconnection or the like, the rotation detection operation can be continued by switching to the second resolver coil 133, using a well-known switcher.
The double resolver structure is a structure employed not only for safety and reliability but also as a multiple speed detector in the field of resolvers. A variety of types of multiple speed detectors have been proposed. Among them, one shown in Japanese Unexamined Patent Application Publication 03-002262 has been proposed in terms of the space occupied. A built-in multi-pole multi-speed rotation detector is structured such that a multiplicity of resolvers, which output different speed signals from each other, are provided in the casing. The resolvers are combined with each other by a random gear ratio with the gear combining portion provided in the casing.
FIG. 6D is a schematic view of the multi-speed resolver of the prior art. As shown in FIG. 6D, the output of the first resolver 1 (142) that is directly connected to the rotation axis 141 becomes the nX resolver signal with a random nX-times axis angle. The output of the second resolver 2 (143) that is connected to the rotation axis 141 via the gear mechanism 144, by which the rotation number of the rotation axis 141 is reduced to 1/n, becomes the 1X resolver signal with a 1X-times axis angle.
FIG. 6E illustrates each of the resolver signals. FIG. 6E indicates the resolver output of the n-rotations of the (mechanical angle) input axis. In this case, the resolver output is a sine wave output, and the relationship between the sine signal wave of the 1X-times axis angle and the sine signal of the resolver with an nX-times axis angle is shown when n=2.
In Japanese Unexamined Patent Application Publication 2001-197610, two resolvers are used. In this device, the space occupied by the resolvers must be larger, and the control of the synchronized operation of two resolvers is difficult.
In Japanese Unexamined Patent Application Publication 2000-018968, the winding range of the stator windings of both resolvers is commonly regulated. Therefore, a problem has been that it is impossible to alternate the multiplied axis angle of the resolvers with each other.
In Japanese Unexamined Utility Model Application Publication 03-002262, there is a gear-combining device, and therefore the generation of a machining error is inevitable. In addition., the gear-combining device is provided on the joint of the axis and therefore, the axial length of the device is increased accordingly.